Oh no, they can end your life too. But only after due process. Thus a death sentence requires a trial and appeals and so on and so forth and takes ages to actually get to the execution. Just keep in mind that chronic lead poisoning does not cause death or even shorten lives. It only reduces IQ and causes behavioral and cognitive disabilities.
If you want safe drinking water you have to provide it yourself. Either dig your own well, or band together with your neighbors to have municipal water. Or buy drinking water from a private company; lots of people in the US do that. Europeans are frequently shocked to learn this, but ironically private water companies have a better track record for safety than municipal water systems. We are, after all, talking about a contamination case involving a municipal water system rather than a private one.
If you dig your own well then you are responsible for ensuring that it remains safe. Regular testing and maintenance is entirely your responsibility. Of course you are allowed to delegate to a contractor, but ultimately the responsibility rests entirely on your shoulders.
If you subscribe to a municipal water system then the responsibility rests on the municipality. You will be electing someone to run the water system. Choose wisely. Your vote has actual physical safety consequences for you and your children. Furthermore you may want to write local ordinances that govern the behavior of this type of elected officials. You might want to be able to rely on them making truthful statements, for example. If so then you should put that in writing in your municipal ordinances. Many states and cities have already done just that! Off hand I don’t know if Mississippi or the city of Jackson have.
Similarly we also have laws and ordinances against the government poisoning people. It is usually illegal, in most jurisdictions, in most circumstances. We also have laws against negligence that leads to harms such as poisoning people.
Just because something isn’t in the Constitution doesn’t mean it’s legal. In this case people seem to have heard that safe drinking water isn’t guaranteed in the Constitution and jumped to the ridiculous conclusion that the government can poison people whenever it wants with no consequences.
The Constitution, and especially the Bill of Rights and other amendments, is mostly a list of things that the government is not allowed to take away from the people or other parts of the government. It’s not a list of all desirable things that the people want governments to do.